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<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy">I don’t think the stub resolver on Linux does any caching of its own. That seems to be born out by this page which mentions that some
newer Windows stub resolvers do:<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy"><a href="http://www.zytrax.com/books/dns/apa/resolver.html">http://www.zytrax.com/books/dns/apa/resolver.html</a><o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy">So it seems if you wanted cache at client level on Linux you’d need to implement something like BIND (or maybe TinyDNS which I haven’t
worked with) and have it get answers from upstream server. More work than I’d want to do for most clients. I’d think if you had a single (or better yet a pair) caching DNS server in your environment and had it in your clients’ /etc/resolv.conf that the
lookups should be quick enough for most purposes without needing to cache at client level.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy">I’ve never used the db option in nsswitch.conf but based on what little I can glean I don’t think it is for hosts but rather for things
like passwd, groups and shadow.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p>
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<p class="MsoNormal"><b><font size="2" face="Tahoma"><span style="font-size:10.0pt;
font-family:Tahoma;font-weight:bold">From:</span></font></b><font size="2" face="Tahoma"><span style="font-size:10.0pt;font-family:Tahoma"> ale-bounces@ale.org [mailto:ale-bounces@ale.org]
<b><span style="font-weight:bold">On Behalf Of </span></b>Chesser.Damon<br>
<b><span style="font-weight:bold">Sent:</span></b> Tuesday, November 01, 2011 12:03 PM<br>
<b><span style="font-weight:bold">To:</span></b> ale@ale.org<br>
<b><span style="font-weight:bold">Subject:</span></b> [ale] nsswitch and db option</span></font><font size="3" face="Times New Roman"><span style="font-size:
12.0pt;font-family:"Times New Roman""><o:p></o:p></span></font></p>
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<p class="MsoNormal"><font size="2" face="Calibri"><span style="font-size:11.0pt"><o:p> </o:p></span></font></p>
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<p class="MsoNormal"><font size="2" face="Calibri"><span style="font-size:11.0pt">I am trying to research the db option in nsswitch (as in: hosts: db files dns ). We figure if a Linux client can use the dns cache for lookups, that would be faster then files
or dns. However, I can’t find anybody who has ever used that option and google is slim pickens researching it.<o:p></o:p></span></font><u5:p></u5:p></p>
<p class="MsoNormal"><u5:p><font size="2" face="Calibri"><span style="font-size:11.0pt"> <o:p></o:p></span></font></u5:p></p>
<p class="MsoNormal"><font size="2" face="Calibri"><span style="font-size:11.0pt">How do you access the (Linux) client dns cache info? Would “hosts: db files dns” cause the first check to be performed on the dns cache?<o:p></o:p></span></font><u5:p></u5:p></p>
<p class="MsoNormal"><u5:p><font size="2" face="Calibri"><span style="font-size:11.0pt"> <o:p></o:p></span></font></u5:p></p>
<p class="MsoNormal"><font size="2" face="Calibri"><span style="font-size:11.0pt">If NOT what does “db” cause to happen?<o:p></o:p></span></font><u5:p></u5:p></p>
<p class="MsoNormal"><u5:p><font size="2" face="Calibri"><span style="font-size:11.0pt"> <o:p></o:p></span></font></u5:p></p>
<p class="MsoNormal"><font size="2" face="Calibri"><span style="font-size:11.0pt">Thanks!<o:p></o:p></span></font><u5:p></u5:p></p>
<p class="MsoNormal"><u5:p><font size="2" face="Calibri"><span style="font-size:11.0pt"> <o:p></o:p></span></font></u5:p></p>
<p class="MsoNormal"><font size="2" face="Calibri"><span style="font-size:11.0pt">Damon.chesser@suntrust.com<o:p></o:p></span></font><u5:p></u5:p></p>
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